1. Field of the Invention
The invention concerns a slab reinforcement with a reinforced concrete column and a slab part made of reinforced concrete or prestressed concrete. The invention further concerns a procedure for the fabrication of such slab reinforcements.
2. Description of the Related Art
Reinforced concrete or prestressed concrete parts, e.g. of a supported slab require shearing check in the form of shear reinforcement in the area of the columns and in other areas.
Known types of shear reinforcement include: shear reinforcement made of reinforcing steel in the form of S-shaped hooks or stirrups, “stud rails”, double-headed studs, stirrup mats, lattice beams, “Tobler” hip, “Geilinger” collar, “Riss” star.
Because of the poor anchorage, a shear reinforcement made of reinforcing steel in the form of S-shaped hooks or stirrups must embrace a mostly existing bending longitudinal reinforcement to prevent the shear reinforcement from tearing out. This is very expensive. In the case of high reinforcement ratios of the bending tensile reinforcement and a high shearing reinforcement ratio, conventional stirrups are regarded as unsuitable.
Stud rails are mostly placed onto the lower formwork, so that the lower layer of reinforcement is encompassed by its cross-section. Exact position and fixing of the rail is decisive for the load bearing performance. The stud rails are welded made-to-order pieces and therefore expensive.
Double-headed studs are usually threaded in from above between the upper and lower layers of the existing longitudinal bending reinforcement. In the case of high reinforcement ratios of the flexural tensile reinforcement and different mesh sizes of the upper and lower layers, this is very difficult and sometimes they cannot be installed. The double-headed studs are made to order and therefore expensive.
Stud rails and double-headed studs are very much used, but series production is not economical because of the high storage costs. Another problem is the danger of confusion and storage of different stud rails and double-headed studs on the construction site.
Tobler hip and collar are steel mounting parts consisting of steel sections welded together and made to order. The bearings structures are to be installed under steelworks conditions and are therefore expensive and labor-intensive. Due to their weight, the mounting parts need to be placed by means of cranes or other hoisting gear.
The functioning of all common solutions depends on concrete as a material. A look at the load paths (path of the shear forces) shows that the load is transferred in and out of the reinforcing elements several times until it reaches the non-critical area. Failure due to shear or compressive fracture, or tearing out of the reinforcing parts can occur.
Therefore, it is one of the objects of the invention, to provide a new slab/ceiling reinforcement and a method for its fabrication.